Method readHeader

src/main/java/com/jmatio/io/MatFileReader.java:1315–1351

Reads MAT-file header. Modifies buf position. @param buf ByteBuffer @throws IOException if reading from buffer fails or if this is not a valid MAT-file

(ByteBuffer buf)

	 *             MAT-file
	 */
	void readHeader(ByteBuffer buf) throws IOException {
		//header values
		String description;
		byte[] endianIndicator = new byte[2];

		// This part of the header is missing if the file isn't a regular mat file.  So ignore.
		if (matType == MatFileType.Regular) {
			//descriptive text 116 bytes
			byte[] descriptionBuffer = new byte[116];
			buf.get(descriptionBuffer);

			description = zeroEndByteArrayToString(descriptionBuffer);

			if (!description.matches("MATLAB 5.0 MAT-file.*")) {
				throw new MatlabIOException("This is not a valid MATLAB 5.0 MAT-file.");
			}

			//subsyst data offset 8 bytes
			buf.position(buf.position() + 8);
		} else {
			description = "Simulink generated MATLAB 5.0 MAT-file"; // Default simulink description.
		}

		byte[] bversion = new byte[2];
		//version 2 bytes
		buf.get(bversion);

		//endian indicator 2 bytes
		buf.get(endianIndicator);

		matFileHeader = MatFileHeader.parseFrom(description, bversion, endianIndicator);
		buf.order(matFileHeader.getByteOrder());

		// After the header, the next read must be aligned.  Thus force the alignment.  Only matters with reduced header data,
		// but apply it regardless for safety.
		buf.position((buf.position() + 7) & 0xfffffff8);
	}

	/**
	 * TAG operator. Facilitates reading operations.